Process vessels lined with refractory concrete, bricks and other ceramic materials are used in a number of applications including in the cement, petroleum, petrochemicals, mineral processing, alumina and other industries. Such process vessels typically comprise an outer shell (usually made from steel or other metal) having a refractory lining. From time to time the linings break down and need to be replaced or repaired. Failure in the lining of a process vessel includes de-bonding of the refractory layers, failure of anchor supports, delamination, voiding, cracking or honeycombing in the refractory layers, and the like.
In order to maintain process vessels that are lined with refractory materials, it is generally necessary for the process vessels to be taken offline and the refractory lining to be inspected and then repaired or replaced as necessary. Taking a process vessel offline for the inspection and repair of refractory linings results in a significant loss of productivity. Certain process vessels may take many hours, or even days, to cool sufficiently or to be in a condition for inspection and repair. The inspection and repair of the refractory lining is also a potentially hazardous operation. Operators enter a process vessel in order to inspect and determine the condition of the lining. Incidents have occurred where linings have fallen from a process vessel while an operator has been inside the vessel. It is desirable to minimize the need for repair of refractory lined vessels.
Process vessels are often lined with a double layer lining system which incorporates an insulation layer and a hot face layer. The insulation layer is supported against the internal wall of the process vessel by refractory anchors. A hot face layer is supported against the insulation layer and again supported by the refractory anchors.
The anchors used for supporting the lining system are generally formed from steel bars and are often V or Y shaped. The V-shaped anchors have their respective arms extending divergently through the insulation layer and into the hot face layer.
In an alternate system for supporting a double layer lining, Y-shaped refractory anchors have also been used. In use, these Y-shaped anchors are attached to the process vessel and extend into the lining. The double-layered lining is cast so that the bifurcation, or apex of the Y, is embedded within the insulation layer or at the interface between the insulation layer and the hot face layer.
Whilst these anchors provide a useful and effective anchoring system for supporting a double-layered lining, the high cost of replacement of the lining, particularly in terms of the downtime of the process vessel, means that more reliable and effective anchoring systems are needed to improve the efficiency of the operation of the process vessels.
The failure of refractory anchors, such as steel refractory anchors, in process vessels, particularly in two layer lining systems (insulation and hot face) generally results from two dominant failure modes that can be described as a creep rupture and yielding.
Creep rupture is due to a small constant load on the anchor and this could be the weight of the refractory castable and/or the thermal load during operation. Creep rupture stress is the load in 1,000, 10,000 or 100,000 hours that will result in failure of the anchor. The higher the load and the higher the temperature, means the time to failure will decrease. Yielding of the anchor is due to an excessive load applied to the anchor during operation. It is normally associated with movement of the hot face castable due to missing or incorrect support/restraint of the castable.
We have now found an anchoring system for a double layer refractory lining for a process vessel that reduces the failure rate of double layer refractory linings and that overcomes or alleviates at least one of the above disadvantages. Other objects and advantages of the invention will become apparent from the following description.